This here says a lot:
http://www.youtube.com/watch?v=E_472L2kLp0
My synopsis: I would never, nor will i let a member of my family, drive a smart car.
Remember, deceleration kills human beings; hence the development of crumple zones to absorb energy and extend the time of the collision thereby decreasing the deceleration rate to sustainable levels (combined with other safety measure such as seat belt improvements and air bags, cars have become exceptionally safe).
Notice that the smart car doesn't just decelerate.... it is accelerated in the opposite direction (add in some other rotational forces and well... you get the picture).
Crash test ratings, as currently used today, are worthless in the grand scheme of things (unless you replace every moving object on the road with a brick wall). So to think that a car (any car.. not just a smart car) is safe based on the "crash test ratings" is a bit short sited. In terms of overall safety, I'll take a 3 star crash test rating in a vehicle like a suburban over a 4 or 5 star crash test rating in a car like the Smart or even the Mini. $.02
Thoughts?